Various scale-magnifying devices have been previously proposed for use directly on a thermometer or on similar elongated instruments, such as barometric instruments, syringes, or the like. These previously proposed scale magnifiers are generally quite cumbersome, are difficult to attach to the instrument, cause scratching or other damage to the surface of the instrument which may obliterate its scale markings, are narrowly limited as to the size of the column on which they can be mounted, are difficult to adjust and read, do not have properly arranged fiducial lines, are relatively fragile, and are costly to fabricate. Typical examples of such previously proposed, directly-mounted mgnifying devices are disclosed in the following prior U.S. Pat. Nos.: Pratesi, 2,351,455; Stegeman, 2,389,282; Tschischeck, 2,586,581; Yin, 3,512,862; Viollet, 3,512,875.
There is a definite need for a directly attachable scale magnifier which does not have the above, and other, shortcomings of the presently known scale-magnifying attachments.